Pneumatic tool lubricant



2,918,429 Patented Dec. 22, 1959.

PNEUMATIC TOOL LUBRICANT Melvin. E. Gililland and Richard C. Givens, Port Arthur,

Tex., assignors to Texaco Inc., a corporation of Delaware NoDrawing. Application November 20, 1956 Serial No. 623,283

7 Claims. (Cl. 252-33.4)

' This invention relates to an improved lubricant for pneumatic tools and more particularly to a lubricating composition having superior lubricating properties which are obtained by means of an additive combination including sulfur, an alkali metal sulfonate, a phosphorus acid ester and mercaptobenzothiazole.

Lubricants employed for the lubrication of pneumatic tools, such as rock drills, are required to have a special combination of properties including non-corrosiveness to copper, good extreme pressure properties in order to protect the tool parts from excessive wear due to high rotational loading, including shock loading, and very superior rust preventiveness to protect the tool parts from rusting under the conditions encountered in drilling operations. Since these lubricants often become contaminated with considerable quantities of water in service, particularly in wet drilling operations, they must have the property of emulsifying readily with water in order to resist being washed away from the lubricated parts.

One type of pneumatic tool lubricants that has been employed commercially has been a compounded mineral oil containing about 10 percent blown rapeseed oil. Because of the expense of blown rapeseed oil, compositions of this type have been excessively expensive for nonrecirculating lubrication of pneumatic tools. Pneumatic tool lubricants based on blownrapeseed oil have the further disadvantage of having a pronounced odor which is particularly objectionable when the lubricant is employed in small enclosed areas. The commonly assigned Bright and Hall Patent 2,734,868 discloses improved pneumatic tool lubricants comprising lubricating oil base containing a special combination of additives comprising a phosphorus acid ester such as tricresyl phosphate, a sulfurized fatty oil such as sulfurized lard oil, a phosphatide emulsifying agent and a polymeric stringiness agent such as a polymerized olefin.

The lubricating composition of this invention, which possesses better extreme pressure and anti-rust properties than the pneumatic tool lubricant disclosed in the aforeidentified Bright and Hall patent, comprises a mineral lubricating oil, 0.05 to 0.15 weight percent sulfur, 0.5 to 2.0 weight percent alkali metal sulfonate, 0.2 to 3.0 weight percent of an oil-soluble phosphorus acid ester and 0.05 to 0.2 weight percent mercaptobenzothiazole. The pneumatic tool lubricant also advantageously contains minor amounts of a high molecular weight polymeric stringiness agent and of an anti-foam agent.

The mineral lubricating oil employed as the base oil in the above compositions is preferably a naphthenic or mixed naphthenic and parafiinic refined oil having a viscosity in the range of from about 100 to about 900 seconds Saybolt Universal at 100 F., although somewhat lower or higher viscosities may be employed to obtain lubricating compositions adapted for unusual operating conditions. Ordinarily, an oil having a viscosity in the range of from about 300 to about 700 seconds Saybolt Universal at 100 F. is most suitably employed.

The mineral lubricating base oil usually comprises 92 to 98 percent of the pneumatic tool lubricant. It has been found that a base oil concentration between about 96 and 98 percent is normally used in the formulation of the lubricants of. this invention.

The sulfur component of the pneumatic tool lubricants of the invention is present in a concentration between 0.05 to 0.15 weight percent of the total lubricant. Sulfur concentrations within the prescribed range impart the desired extreme pressure and anti-wear properties tothe.

pneumatic tool lubricants. A preferred sulfur concentration is in the range of 0.08 to 0.12 weight percent. Sulfur concentrations above the 0.15 weight percent level seriously degrade the copper corrosion properties of the, lubricants.

The sulfur is blended into the mineral oil base by a simple procedure involving raising the temperature of the mineral oil base to 220 to 300 F, adding the sulfur and continuing the heating for a minimum period of about hour. The preferred procedure for blending of the sulfur into the mineral oil involves adding the mercapto benzothiazole corrosion inhibitor to the mineral oil, heating the mineral oil to about 250 F. with stirring, adding the sulfur after the mercaptobenzothiazole is dissolved, and maintaining the stirred mixture at about 250 F. for about 30 minutes. During the stirred cooling of the mixture, the alkali metal sulfonate, the phosphorus acid ester, the high molecular weight polymeric stringiness agent and the anti-foam agent are added.

The phosphorus acid ester is a compound chosen from the well-recognized class of extreme pressure compounds which comprises oil-soluble or oil-miscible esters of phosphoric and phosphorous acids, including alkyl, aryl and mixed alkylaryl esters. The term phosphorus acid ester as employed herein will be understood to mean a compound represented by the following formula:

wherein R is hydrogen or an aliphatic, aromatic or alicyclic hydrocarbon group, with at least one R being hydrocarbon, and X is either an oxygen atom or is absent. Substituent groups such as basic groups which have a. deleterious eifect upon the extreme pressure properties of the compound should be absent. As examples of suit: able compounds of this class may be mentioned dilauryl phosphate, tributyl phosphate, triamyl phosphite, tricresyl phosphate, tricresyl phosphite, tricyclohexyl phosphate, trixylyl phosphate, trixylyl phosphite and dioctyl phos phate. Tricresyl phosphate is a particularly effective and readily available material of this character and may be regarded as the preferred compound for use in the lubrieating compositions of the present invention. The phosphorus acid ester may be employed in amounts ranging from about 0.2 to 3 percent, and most suitable froni about 0.5 to 2 percent by weight of the lubricating composition.

The alkali metal sulfonate component, which improves the emulsiiication properties of the lubricant, constitutes 0.5 to 2.0 weight percent of the total lubricant with concentrations between 0.7 and 1.5 weight percent normally being employed. The alkali metal sulfonate is normally derived from a petroleum sulfonic acid which is pro: duced by the reaction of concentrated sulfuric acid with a mineral lubricating oil fraction. Alkali metal salts of alkaryl sulfonic acids such as C alkyl benzene sulfonic acid and dinonyl benzene sulfonic acid may also be used to improve the emulsification properties. Even though sodium petroleum sulfonate is normally used because of its availability and lower cost, other alkali metal sulfonates, such as sodium dinonyl benzene sulfonate, potassium petroleum sulfonate and lithium petroleum sulfonate may be used.

The high molecular weight polymeric stringiness agent may be a polymerized olefin or a polymerized oxygencontaining material such as polymers of vinyl ethers or polyesters of substituted fatty acids. Isobutylene polymer having a Saybolt Furol viscosity at 210 F. of about 1,000 to 2,000 seconds is particularly suitable for this purpose. Such polymeric material may be employed in amounts ranging from about 0.1 to about 3.0 percent by weight of the composition.

The desired anti-corrosive properties, particularly protection against copper corrosion, are imparted to the pneumatic tool lubricant of the invention by the incorporation of 0.05 to 0.2 weight percent mercaptobenzothiazole or a homolog thereof. The usual concentration of mercaptobenzothiazole is about 0.1 weight percent.

The pneumatic tool lubricants of the invention also advantageously contain a suitable amount of anti-foam agent since there is the possibility of air entrainment due to the high speed at which the pneumatic tools operate. For this purpose a silicone polymer of high viscosity, such as dimethyl silicone polymer having a kinematic viscosity at 25 C. of about 1,000 centistokes and above, is preferably employed, since this agent also desirably increases the flash point of the fluid. A silicone polymer is conveniently employed in the form of a concentrate in a hydrocarbon solvent such as kerosene. .For example, a very satisfactory anti-foam agent for this purpose is prepared by diluting 10 grams of a dimethyl silicone polymer (1,000 centistokes at 25 C.) with kerosene to bring the volume to 100 cubic centimeters. A proportion of the order of 0.001 to 0.025 percent by weight of the foregoing concentrate is ordinarily employed, which amount is sufficient to provide about 5 to 200 parts per million of the silicone polymer concentrate on the basis of the pneumatic tool lubricant.

We have found that lubricants of the above composition emulsify readily with water to form emulsions of good lubricating properties and in addition they are characterized by high load carrying and other properties, such as adhesiveness, oiliness, etc., necessary to maintain good lubrication under the severe conditions encountered in rock drilling, including high loads, rapid mechanical jarring, impingement of high velocity gases and large temperature variations. They have the further advantage of being obtained from relatively inexpensive and readily available materials and are substantially free from objectionable odor.

The preparation of the novel pneumatic tool lubricants of this invention is illustrated in the following examples:

EXAMPLE I To a reaction vessel there were charged 10.19 pounds of naphthene base distillate having an SUS viscosity at 100 F. of 210 and 14.07 pounds of a lightly acid-treated naphthene base distillate having an SUS viscosity at 100 F. of about 1151. The resulting oil mixture was raised to a temperature of about 250 F. and 11.3 grams of mercaptobenzothiazole was added. After the mercaptobenzothiazole was dissolved, which took approximately /2 hour, 11.3 grams of sulfur was added and the reaction mixture maintained at about 250 F. until all the sulfur was dissolved, which took approximately hour. 142 grams of a concentrate containing 63 weight percent sodium petroleum sulfonate dissolved in a light naphthene base oil, 113 grams of tricresyl phosphate and 57 grams of an isobutylene polymer having a Saybolt Furol viscosity at 210 F. of about 1,000 to 2,000 seconds were then added to the reaction mixture with stirring. The resulting pneumatic tool lubricant had the following composition:

Percent by wt. Mineral nil 97.51 Sulfur 0.1 Isobutylene polymer 0.5 Sodium petroleum sulfonate 0.79 Tricresyl phospha 1.0 Mercaptobenzothiazole 0.1

EXAMPLE II EXAMPLE III In this example a two-drum batch of a pneumatic tool lubricant having a composition substantially identical with the product of Example I was prepared for field trial. After 177 pounds of a naphthene base distillate having an SUS viscosity at 100 F. of 210 was charged to a reaction vessel, the mixture was raised to a temperature of about 250 F. with stirring and 0.85 pounds of mercaptobenzothiazole was added. When all the mercaptobenzothiazole was in solution, which took about 1 hour, 0.85 pound of sulfur was added and the reaction mixture maintained at about 250 F. for about 30 minutes at which time the sulfur appeared to be in solution. 10.63 pounds of a concentrate comprising 63 weight percent sodium petroleum sulfonate dissolved in a light naphthene base oil,

4.25 pounds of an isobutylene polymer having a Saybolt Furol viscosity at 210 F. of about 1,000 to 2,000 seconds, and 8.5 pounds of tricresyl phosphate were added and the resulting mixture cooled with stirring. At a temperature of about 200 F. 412 pounds of a naphthene base distillate oil having an SUS viscosity at 100 F. of about 1151 and 168.5 pounds of a naphthene base distillate having an SUS viscosity at 100 F. of 210 were added. Finally, 3.86 grams of a kerosene concentrate containing 10% dimethyl silicone polymer was added followed by 67.4 pounds of a naphthene base distillate oil having an SUS viscosity at 100 F. of about 1151. The resulting product had the following composition:

- Mineral oil percent by wt 97.51 Sulfur do 0.1 Isobutylene polymer do 0.5 Sodium petroleum sulfonate do 0.79 Tricresyl phosphate do 1.0 Mercaptobenzothiazole do. 0.1 Kerosene concentrate of dimethyl silicone polymer p.p.rn 10 EXAMPLE IV A pneumatic tool lubricant was prepared by the procedure outlined in Example I to have a sulfur concentration of 0.2 weight percent. The resulting lubricant, which did not contain tricresyl phosphate, had the following composition Table PERFORMANCE TESTS ON PNEUMATIC TOOL 5 LUBRICANTS Examples I II III IV SAE, 500 r.p.rn 230 227 207 303 Almen Value, Avg 25 10%? Humidity Cabinet, Hrs. to

sandblasted 360 192 240 360 Polished 168 72 SUS viscosity at 100 F- 504 621 ORG Foam 'lest:

10-0 10-0 10-0 Neg. +7

The data in the foregoing table indicate that the lubricants of Examples I to IV possess good extreme pressure properties as measured by the SAE and Almen tests and good rust or corrosion protection properties as measured by the humidity cabinet test. Since the lubricants of Examples 1, II and III do not corrode copper as evidenced by their negative rating in the copper strip corrosion test, they are excellent pneumatic tool lubricants from all standpoints. In contrast, the product of Example IV has an excessively high copper corrosion and according- 1y is an unsatisfactory pneumatic tool lubricant. The necessity of using a maximum sulfur concentration of 0.15 percent in order to produce satisfactory pneumatic tool lubricants is proven by the data on the copper corrosion properties of the lubricants of Examples I to IV.

Since field performance is more critical in establishing the value of pneumatic tool lubricants than the foregoing performance tests, the product prepared in Example III was field tested with the following outstanding results: Eight drills of varying manufacture (Ingersoll Rand, Gardner-Denver and Chicago Pneumatic) employed in an iron mine were lubricated with the rock drill lubricant of Example III and provided excellent lubrication. The rock drill lubricant of Example III was judged to give superior performance to competitive products and to the sulfurized lard oil based lubricant disclosed in the afore-identified Bright and Hall patent.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A pneumatic tool lubricant consisting essentially of a mineral lubricating oil having an SUS viscosity at F. from about 100 to about 900, containing about 0.05 to 0.15 weight percent sulfur dispersed in said mineral oil, 0.5 to 2.0 weight percent alkali metal sulfonate, 0.2 to 3.0 weight percent of a phosphorus acid ester selected from the group consisting of oil-soluble and oilmiscible di and trialkyl, aryl and mixed alkyl-aryl phosphates and phosphites, and 0.05 to 0.2 weight percent of a mercaptobenzothiazole corrosion inhibitor.

2. The pneumatic tool lubricant of claim 1 containing 0.1 to 3.0 weight percent of a high molecular weight polymeric stringiness agent selected from the class consisting of olefin polymers, vinyl ether polymers and polyesters of substituted fatty acids, said stringiness agent having a Saybolt Furol viscosity at 210 F. of about 1,000 to 2,000 seconds.

3. The pneumatic tool lubricant of claim 1 wherein the phosphorus acid ester is tricresyl phosphate.

4. The pneumatic tool lubricant of claim 1 wherein the alkali metal sulfonate is sodium petroleum sulfonate.

5. A pneumatic tool lubricant consisting essentially of a mineral lubricating oil distillate having an SUS viscosity at 100 F. between 300 and 700, containing about 0.08 to 0.12 weight percent sulfur dispersed in said mineral oil by heating to a temperature of 220300 F. for a period of about 4 hour 0.7 to 1.5 weight percent alkali metal sulfonate, 0.5 to 2.0 weight percent of an oil-soluble aryl phosphate, 0.05 to 0.2 weight percent rnercaptobenzothiazo-le, 0.1 to about 3.0 weight percent isobutylene polymer having a Saybolt Furol viscosity at 210 F. of about 1,000 to 2,000 seconds, and 5 to 200 parts per million of a silicone polymer concentrate as an anti-foam agent.

6. The pneumatic tool lubricant of claim 5 wherein the phosphorus acid ester is tricresyl phosphate.

7. The pneumatic tool lubricant of claim 5 wherein the alkali metal sulfonate is sodium petroleum sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS 1,913,300 Abrams June 6, 1933 2,349,224 Nill May 16, 1944 2,533,700 Wasson Dec. 12, 1950 2,638,446 Wallace May 12, 1953 2,655,478 Deutser et al Oct. 13, 1953 2,669,560 Sperry Feb. 16, 1954 2,734,868 Bright et al. Feb. 14, 1956 2,744,083 Moody et al May 1, 1956 2,764,547 Fields Sept. 25, 1956 FOREIGN PATENTS 616,881 Great Britain Jan. 28, 1949 

1. A PNEUMATIC TOOL LUBRICANT CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL HAVING AN SUS VISCOSITY AT 100*F. FROM ABOUT 100 TO ABOUT 900, CONTAINING ABOUT 0.05 TO 0.15 WEIGHT PERCENT SULFUR DISPERSED IN SAID MINERAL OIL, 0.5 TO 2.0 WEIGHT PERCENT ALKALI METAL SULFONATE, 0.2 TO 3.0 WEIGHT PERCENT OF A PHOSPHORUS ACID ESTER SELECTED FROM THE GROUP CONSISTING OF OIL-SOLUBLE AND OILMISCIBLE DI AND TRIALKYL, ARYL AND MIXED ALKYL-ARYL PHOSPHATES AND PHOSPHITES, AND 0.05 TO 0.2 WEIGHT PERCENT OF A MERCAPTOBENZOTHIAZOLE CORROSION INHIBITOR. 